1. Field of the Invention
The invention relates to the field of multi-channel audio transmission and to systems and methods of providing a plurality of user selectable dialog channels in a multi-channel audio transmission.
2. Description of the Related Art
Increasing technical capabilities and user preferences have led to a wide variety of audio recording and playback systems. Audio systems have developed beyond the simpler stereo systems having separate left and right recording/playback channels to what are commonly referred to as surround sound systems. Surround sound systems are generally designed to provide a more realistic playback experience for the listener by providing sound sources that originate or appear to originate from a plurality of spatial locations arranged about the listener, generally including sound sources located behind the listener.
A surround sound system will frequently include a center channel, at least one left channel, and at least one right channel adapted to generate sound generally in front of the listener. Surround sound systems will also generally include at least one left surround source and at least one right surround source adapted for generation of sound generally behind the listener. Surround sound systems can also include a low frequency effects (LFE) channel to improve the playback of low frequency sounds. As one particular example, a surround sound system having a center channel, a left front channel, a right front channel, a left surround channel, a right surround channel, and a LFE channel is referred to as a 5.1 surround system.
One feature that is frequently desired in audio recording and playback is to have the audio available in multiple languages. For example, sports coverage, theatrical movies, video news reports, and many other types of audio content is of interest to a wide variety of people who may speak a corresponding wide variety of languages and/or local dialects. This need is frequently addressed in pre-recorded material by dubbing in a desired language channel with background or non-dialog audio, such as environmental sounds, engine noises, gunfire and explosions, crowd noise, etc. that would also be included with alternative audio with other languages. Thus, a consumer may watch pre-recorded programming stored on a storage medium such as a DVD and, upon play of the programming, select the desired language. For example, a user may select between English, French, and Spanish. Such systems typically require that the user select the desired language for the audio upon initial playback of the recorded programming. If the user subsequently wishes to select a different language, the systems generally require that the user halt the playback of the programming, select an alternative language, and restart playback of the programming.
In broadcast transmission of audio programming, it is known to provide a secondary audio programming (SAP) that a user can select to obtain a second alternative audio signal. A drawback to such systems are, however, that the listener is provided with a choice of only two language options, e.g., the primary and a single secondary audio option. A further drawback is that while the primary audio option is often provided in a stereo format, the secondary audio programming is typically limited to a monaural audio signal. Thus, a user desiring the secondary language option is not provided with the improved listening experience provided by multi-channel audio.
The approach taken with pre-recorded audio content that is subsequently replayed, for example DVD recordings, is not feasible with real-time streaming or broadcast transmission as such systems do not provide sufficient bandwidth to support multiple multi-channel audio signals. It will thus be appreciated that there exists a need for improved systems and processes for transmitting audio signals to allow an end user or recipient to have the option of multiple dialog choices while continuing to enjoy the audio experience of multi-channel surround sound. There is a particular need for dialog options in surround sound systems that can be employed in streaming or broadcast manner, for example, Internet streaming, broadcast television, cable television, and satellite television transmission.